Material for providing traction



Patented Nov. 12, 1946 UNITED STATES A PATENT OFFICE MATERIAL FORPROVIDING TRACTION Bertrand H. Wait, New Rochelle, N. Y.

No Drawing. Application March 27, 1944,

a Serial No. 528,367 I 2 Claims. (Cl. 117-100) My invention relates toimprovements in matecause it does not penetrate the ice and is quickly.

picked up and scattered by wind, traflic or both.

On the other hand the application .of salts alone to the ice does notquickly; provide a surface which is sufiiciently rough to affordtraction for motor vehicles and the high cost of such materials in thequantities necessary to produce rapid and thorough disintegration of theice is prohibitive;

A further advance in the art was made more or less incidentally whensuch salts were added to stock piles of sand, screenings andthe like toprevent their freezing into a solid mass. When abrasive material withsuch additions is spread on the surface of the ice the salt tends tomelt the ice and thus permit the abrasive particles which happen to lieclosely adjacent particles of the salt to stick to said surface orbecome partially embedded therein. The quantity of salt usually employedto prevent the stock piles from freezing into a solid mass is not verygreatand ordinarily it is merely deposited in flake form in the pile asit is built up or on top of the pile and becomes distributed more orless unevenly therethrough only as it deliquesces or as the trucks fromwhich the material is spread are loaded from the pile. Thus, manyparticles of abrasive are deposited on the ice with little or nothing tofacilitate their penetration and anchorage therein.

In order to prevent the freezing of stock piles of sand and to provide afree flowing material it has been proposed to treat the sand with asolution of calcium chloride. and to apply the wet material to the ice.Such a material is very heavy due to the large volume of water therein;the quantity of salt associated with each particle of abrasive is verysmall; and its association with the particle is brief. For these reasonssand, screenings and the like so treated are not appreciably effectivein producing disintegration of the ice. Such material produces somewhatbetter eneral results than salts alone or abrasives alone but it doesnot help materially in the disintegration of the ice which is highlydesirable if such a result can be obtained economically because, whendisintegrated, the ice can be easily removed from .the road by scrapers.

Ordinarily the extent to which the abrasives Will become embedded in theice is a function of the temperature andthe quantity of salt. Be-' causetemperatures vary over wide ranges it is impossible to foretell thetemperature which may be encountered in any instance. When too small aproportion of salt is employed the ice is not softened sufliciently forthe particles of abrasives to embed themselves and they are blown awayor scattered by traffic. On the other hand, when too great a proportionof salts is employed the ice melts rapidly, the abrasives lie in Water,little traction is obtained, some of the abrasives are flushed off thesurface and, eventually, the solution becomes so dilute that itrefreezes with a tractionless surface and requires replacing.

The principal object of my invention is to provide an improved materialfor providing traction on icy pavements and at the same time to providea material which will effectively disintegrate the ice. Another objectis to provide a material of this character which is comparatively lightin weight so that handling and shipping costs are reduced. A furtherobject is to provide a material which can be economically produced, andWhich will be effective over longer periods of time than the materialsnow employed for this purpose.

base a porous absorptive material such as slag or cinders in the form ofdiscrete particles. Depending upon the form in which the material isavailable, it is either crushed and thereafter screened, or merelyscreened, to reject all particles which will not pass through a one-halfinch square opening. A fairly large percentage of fine mat rial ispreferable since such material, in the aggregate, presents a muchgreater surface area for the adsorption of the salts which are to beapplied than the same weight of material in larger sizes, and thesmaller material is more effective in initiating disintegration of theice over a greater area. Material which is larger than about one-halfinch in size is undesirable because the object is to produce a materialwhich will not only stick to the ice but will initiate disintegration ofthe ice at the largest possible number of points.

If the screened material is wet Or contains any I accomplish theseobjects by employing as a 3 substantial quantity of moisture it is thendried, preferably by heating.

After drying, the material is impregnated and incidentally coated bytreating it in or with an aqueous solution of a salt, such as calcium orsodium chloride, or both, adapted to lower the freezing point of Water.The material is preferably treated by spraying the solution on the driedparticles which may be, and preferably are, still hot from the dryingstep. However, the solution may be poured on the material, or thematerial may be immersed in or run through a bath of the treatingsolution. The strength of the solution may vary depending upon thetemperature expected to be encountered in the application. Where thesetemperatures are very low I prefer to use a substantially saturatedsolution. The particles quickly absorb and adsorb the chlorides, and thetreated material may be used immediately or stock piled for future use.However, in all cases, and especially where shipping or handling costsbased on tonnage are high, the material is preferably dried to effect arecrystallization, 01' at least partial recrystallization, of the saltsby heating. During the drying, the material should be agitated toprevent the formation of solid masses. This can be easily done in aheater of the well known type used for heating and drying a gregatesprior to incorporating bituminous materials therewith, 7

When the material is spread, the coating on the outside of the particlescomes into contact with the ice and melts or softens the icesufficiently to create pockets into which the particles embedthemselves. The advantages of using an impregnated, porous, basematerial now becomes evident. Such material, thereafter, releases slowlythe salts with which it is impregnated and offers a marked resistance tothat rapid dilution of the salt solution which occurs where theabrasives are only surface treated. Since the particles are almostimmediately partially embedded in the ice they are not easily scatteredby Wind and traffic and, in time, work their way down through the icehoneycombing it and facilitating its removal by scrapers, oraccelerating the disintegrating effects of the natural forces such assun rays or a rise in atmospheric temperature.

Calcium chloride gives much quicker action than sodium chloride andhence there is some advantage in treating the material with a solutionof each separately or together, thus obtaining the quick action of thecalcium chloride for immediate contact with the ice and the slow actionof the sodium chloride contained by the aggregate for the rotting of theice. Thus, assuming for example, that a water cooled pulverized slag,which is very porous, is the material treated: After screening I mayfirst impregnate the slag palticles with a solution of sodium chlorideor a mixture of sodium and calcium chloride, dry them, and thereafterlightly spray the particles with a solution of calcium chloride, thusproviding on the surface of the particles a small quantity of asubstance which acts quickly to anchor the particles to the ice and, atthe same time, providing a slower acting material in the sodium chloridewhich effectively rots the ice and gradually e beds the particlestherein.

As a general rule the solutions used will be highly concentrated saltliquids which will be absorbed by the particles and provide a maximumproportion of the salts per ton of material, thus doing away with highcost of shipping and handling to obtain satisfactory results.

It will be apparent that by using a substantially saturated solution,which may be heated to increase the quantity of salt which can becarried thereby, and then applying it to heated particles of any waterinsoluble material, such as stone screenings, any cooling of the treatedmaterial or any evaporation of the Water from the material, as by a hotdrying process, will effect a precipitation of some of the salt on thearticles. Thus, a material is provided having a coating of a saltthereon at least partially in solid or crystalline form which will beparticularlyeffective, irrespective of the degree of impregnationbecause substantially all of the salt will be concentrated on theparticles where it will function to anchor them individually in the ice.

What I claim is:

1. The method of forming a material for providing traction on icypavements which comprises impregnating a hard, porous water-insolublesubstance in the form of discrete particles with sodium chloride bytreating said particles in a solution of said salt, drying saidparticles to effect at least a partial recrystallization of said salt,and thereafter spraying said particles with a, solution of calciumchloride.

2. The method of forming a material adapted to provide traction on icypavements upon its application thereto which comprises impregnatingporous slag in the form of discrete particles with a hot saturatedsolution of calcium chloride and thereafter cooling said particles toeffect a precipitation and recrystallization of said calcium chloride inand on said particles.

BER'I'RAND H. WAIT.

